This invention relates generally to a method for designing a fixture to hold a material to be welded during a weld process and, more particularly, to a method for modeling a simulated weld fixture to determine reaction forces produced by the weld process.
Welding a material is a common and well known procedure in a manufacturing process. The material being welded, typically a metal of some type, is altered by the weld process into a form that may be at least as strong as the original material to be welded. Many industries, e.g., manufacturers of mobile machines such as earthworking machines, transport machines, and the like, rely on welding as an integral part of the manufacturing process.
The welding process, however, creates undesirable side effects in the material to be welded. Distortions occur from the intense heat being used, and the resultant material may not maintain the desired shape when welding is completed.
Therefore, in the welding industry, it is common to employ techniques prior to the weld process which induce distortions in the material which are essentially the opposite as the distortions induced by the welding process. The intent of these induced distortions is to cause the material, during welding, to distort back to the original desired shape. For example, a technique known as pre-cambering, i.e., bending the material into a temporary distorted shape, is often used. Pre-cambering is accomplished by placing the material into a weld fixture, which holds the material in the desired distorted shape until welding is completed.
However, a weld fixture of this type must be designed to withstand reactive forces from the mechanical distortions induced on the material, and from thermal distortions produced by the weld process. These forces are of varying magnitude at different locations on the fixture, and the magnitude varies with time during welding. It is difficult to properly design a weld fixture to withstand these reactive forces at the proper locations on the fixture. Therefore, typical weld fixtures are either under-designed or over-designed. If a fixture is under-designed, the fixture will break during welding and a new fixture must be designed and built. This trial and error method is very costly. On the other hand, the fixture may be over-designed to avoid breakdown. This method, however, is also very costly since the fixture is built to much higher tolerances than needed.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention a method for designing a weld fixture is disclosed. The method includes the steps of modeling a set of distortions produced by applied mechanical forces on a material to be welded, modeling a set of distortions produced by applied thermal forces on the material to be welded, determining a set of reaction forces at a series of locations on a simulated weld fixture as a function of the modeled distortions, and designing a weld fixture as a function of the set of reaction forces.